1. Field of the Invention
The invention relates to providing a supply of ink via tubing to ink jet print heads in an ink jet printer.
2. Description of the Related Art
In many ink jet printers, sealed ink jet cartridges containing a fixed supply of ink are utilized. The cartridges are passed over the paper, and ink is ejected from the cartridge to form the image. When the ink in a particular cartridge has been depleted, the cartridge is replaced. To maximize print head use, some printers incorporate separate stationary large volume ink supplies, and the ink in these supplies is routed via tubing from the external supply to the print cartridges. One system of this type is described in U.S. Pat. No. 5,686,947 issued on Nov. 11, 1997. The disclosure of this patent is hereby incorporated by reference in its entirety.
Print quality is highly dependent on accurate ink droplet placement on the media. Accordingly, any deviations in print head position during printing (other than the desired print head scanning motion across the media) can result in inaccurate drop placement and/or size, and thus reduce image quality.
One source of print head position variation can arise from the ink supply tubing that is connected to the moving carriage that holds the ink jet cartridges. External forces from the ink supply tubing can be transmitted to the carriage, causing vibrations and other positional deviations of the cartridges as they pass over the media. In some printer embodiments, the weight of the ink supply tubing that is supported by the carriage varies with carriage position from one side of the printer to the other. In these cases, the carriage can be forced to rock backward and forward around its support shaft as the weight of the tubing increases and decreases during passes over the media. Because this positional deviation is consistent with carriage location during a scan, print errors caused by this problem appear as visible vertical banding in the printed image.
In one embodiment, the invention is directed to a method of reducing drop position errors during ink jet printing comprising separating a movable print carriage into first and second rotationally de-coupled portions and mounting ink applicators to only one of the portions. In a specific embodiment, a device for use in an ink jet printer for mitigating ink drop placement error caused by the weight of various carriage components comprises first and second carriage portions, the first carriage portion being configured to receive a plurality of ink jet cartridges, and the second carriage portion being configured to couple to a cable chain adapted to support ink supply tubing. In this embodiment, the first and second carriage portions are non-rigidly coupled such that they are substantially coupled in linear motion along a common axis, and substantially de-coupled in rotational movement about the axis.
In another embodiment, an ink jet printer comprising first and second carriage portions movably mounted on a guide rod, the first carriage portion being adapted to receive at least one ink jet cartridge, and the second carriage portion being mounted to the guide rod by first and second side plates positioned adjacent to corresponding first and second ends of the first carriage portion whereby axial movement of the first or second carriage portion will cause corresponding axial movement of the other carriage portion; and whereby the first and second carriage portions are rotationally independent.
The invention also includes a method of making an ink jet printer comprising mounting first and second carriage portions on a guide rod such that the second carriage portion is substantially rigidly mounted on side plates which are moveably mounted on the guide rod, and the first carriage portion is moveably mounted on the guide rod interjacent the side plates.